Thanks for the reply.
To be precise,
whichever face I select as fixed face while running the macro,
it does not consider my selection. The flat pattern is created from a default face by solidworks.
I have attached some images for a better understanding, hope this should help us.
The actual need is,
While creating the Flat Pattern using the Macro,
The user should have the freedom of selecting the fixed face for the Flat Pattern based on his needs.
Just edit the Flatt-Patter feature and select the face you want to become the default fixed face for Flatt-Pattern.